I don't think voles and moles get in each other's way when foraging (or only if, by chance, they both happen to want to use the same tunnel). As far as I know, voles are vegetarians with a preference for roots (which is why these critters cause me so much trouble in the garden), while moles eat insects and other invertebrates.
Well, in any case, thanks for your input... let’s see if the “trample the tunnels” tactic works.